Electrical system of power transmission



J. R. CRAIGHEAD AND H. R. SUMMERHAYES.

ELECTRICAL SYSTEM OF POWER TRANSMISSION.

APPLICATION FILED APR. 17. I919- Patented Aug. 24, 1920.

2 SHEETS-SHEET 1- Inventor-s:

I 1%; Then" fittor-neg.

s i mm m re m flu e mR s r h e H .I. R. CRAIGHEAD AND H. R. SUMMERHAYES.

ELECTRICAL SYSTEM OF POWER TRANSMISSION.

' APPLICATION FILED APR. 11. 1919.

1 3 5 O, 9 2O Patented Aug- 24, 1920.

2 SHEETSSHEET 2.

Load. -7 Ill/ll Inventor-s: James R.C1"aighead Hew'wr- R.Sum' erhaygs, by

Their I tLoTneg OFFICE.

.JAMES B. CRAIGHEAD AND HENRY a sUMM nHAYEs, or SCHENECTADY, NEW Yonx, ASSIGNORS TO GENERAL ELECTRIC COMPANY, A conromrron' -or NEW YORK.

ELECTRICAL SYSTEM OF POWER TRANSMISSION. I

Application filed April 17, 1919. Serial No. 290,687.

To all whom it may concern:

Be it known that we, JAMES R. CRAIG- HEAD and HENRY R. SUMMERHAYES, citizens of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Electrical Systems of Power Transmission,-of which the following is a specification.

This invention relates to electrical systems of power transmission and particularly to electrical systems of power transmission comprising a distribution system and a main source of alternating current including one or more generating stations.

In transmission systems of the kind referred to, it is common to connect the distribution system to the main source so that energy is transferred therebetween at a plu-.

- trolling electrical apparatus so that it will operate responsive to a function of the product of the voltage and watt component of the current supplied to the distribution system by the source, or to a function of the product of the voltage and wattless component of the current supplied to the distribution system by the source, or to a function of both products.

In such transmission systems it is sometimes desirable to have available at a main place an arrangement, by means of which the amount, the power factor, or both the amount and the power factor, of the load imposed upon the main source by the distribution system or, in case the distribution,

system returns energy to the main source, as in an electric railway system where regenerative braking is used, the. amount, power factor, or both the amount and the power factor, of the load imposed upon the distribution system will'be indicated. It 18 ordinarily not feasible to conduct the energy interchanged between. the main source and the distribution system through a main place or station for the purpose of measurement or indication The necessity of doing this, however, is avoided by means of our invention, another object of which is to provide a new and improved system whereby the amount, the power factor, or the amount and the power factor, of the load imposed which is drawing energy therefrom, may be indicated, and also whereby the amount, the power factor, or both-the amount and power factor, of the load imposed upon said distribution system, when it is returning energy to the source, may be indicated.

In transmission systems of the kind referred to, it is also often desirable to maintain the power factor of the load imposed upon the main source of alternating current by the distribution system approximately constant and it may also be desirable to Specification of Letters Patent. Patented A g i 1920 limit the amount of the load to a predeter- V mined maximum value. 'This'is particularly apt to be the case where the distribution system is supplied with purchased energy and where the purchase rate is made to depend upon the power factor and maximum value of .the load imposed upon the main source by the distribution system.

Another object of our invention, therefore, is to provide a new and improved system whereby the power factor of the load imposed upon a main source of alternating current by a distribution system is automatically maintained approximately constant.

Still another object of our invention is to provide a new and improved system whereby the power factor of the load imposed upon a main source of alternating current by a distribution circuit is automatically maintained approximately constant and whereby the amount of such load is limited to a predetermined maximumvalue.

Our invention may best be'understood by reference to the following description when considered in connection with the accompanying drawings, while the scope of our,

invention is defined in the claims appended hereto.

Referring to the accompanying drawings, in Figure 1 of which is diagrammatically shown a system, embodying one embodiment of our invention, for automatically controlling the power factor and the amount of the load imposed upon a main source of alternating current by a distribution system, and in Fig. 2 of which is diagrammatically shown a system, embodying another embodiment of our invention and comprising a, main source of alternating current and a distribution system, for indicating the power energized from one or more main generating stations 5. 6 and 7 denotes substations having leading-in conductors 8 and 9 which are adapted to be connected to the feeder mains 2 by means of switches 10 and 11. The leading-in conductors 8 and 9,-at the stations 6 and 7, are connected to suitable substation apparatus, illustration of which, for a the sake of simplicity and clearness, is omitted from the drawing, the legend load being applied to the substation ter-- minals of the leading-in conductors 8 and 9 instead. 12 denotes a supplemental steam station comprising a steam turbine 13 and a three-phase generator 14. The generator 14 comprises a rotating field 15, connected to be driven by the turbine, and a station-v ary armature 16, which is adapted to be connected, by means of the switch 17 and the feeder mains 18, to the leading-in conductors 8 and 9 at the substations 6 and 7. The turbine 13 is provided with a centrifugal governor comprising a lever 19, connected to control a throttle valve 20, a pair of centrifugally operated weights 21 for actuating the lever 19, a spring 22 for opposing the movement of the lever 19 by the centrifugal weights 21, a screw 23, and a worm gear 24 cooperating therewith for adjusting the tension of the spring 22. 25 denotes a reversible motor having an armature 26, connected to the gear 24 and field windings 27 and 28. 29 represents a contact making ammeter having a current winding 30, a switch blade 31 actuatedthereby, an adjustable spring 32 for opposing the movement of the switch blade 31 in response to the influence of the current winding 30, and stationary contacts 33., 34 and 35. 36 denotes a direct current generator to the positive side of which the lower brush of the armature 26 is connected, while the upper brush of the armature 26 is connected to one terminal of each of the field windings 27 and 28. The opposite terminals of the'field windings 27 and 28 are connected to the stationary contacts 34 and 35 of the contact making ammeter 29, and the stationary contacts 33 are connected to the negative side of the generator 36. With the connections as shown, when the current in the winding 30 ofthe contact making ammeter 29 is below a predetermined value,

the switch blade 31 will bridge the stationary contacts 33 and 35, thereby causing the armature 26 of the motor 25 to rotate in a direction such that the tension of the spring 22' will be decreased, whereas, when the current in the Winding 30 is. above said predetermined value, the switch blade 31 will bridge the stationary contacts 33 and 34, thereby causing the armature 26 of the motor 25 to rotate in the reverse direction so as to increase the tension ,of the spring 22. 37 denotes a motor operated rheostat comprising a variable resistance 38, controller arm 39 for varying said resistance, and a reversible motor 40 for actuating the controller arm 39. The motor 40 comprises an armature 41, connected through gearing to the controller arm 39, and field windings 42 and 43. One brush ofthe armature 41 is electrically connected to the positive side of the generator 36 and the other brush is connected to one terminal of each of the field windings 42 and 43. One collector ring of the rotating field 15 is connected through the variable resistance 38 of the motor operated rheostat 37 to the positive side of the generator 36, whereas the other collector ring of the rotating field 15 is connected to the negative side of the generator 36. 44 denotes a contact making instrument comprising fixed coils 45 and 46, which are preferably angularly displaced ninety degrees, and a pivoted coil 47 cotiperating therewith. The coil 47 carries a contact 48 which is adapted to engage with contacts 49 and 50 which are adjustably mounted on a member 51, the position of which may be angularly adjusted by means of a screw 52, and are electrically connected to the terminals of the field windings 42 and 43 of the motor 40 opposite to those terminals to which one brush of the armature 41 is connected. The contact 48 is connected to the negative side of the generator 36. The coil 47 is directly connected across the terminals of the generator 36. 53 and 54 denote control circuits having a common return con ductor 55. The positive side of the generator 36 is connected, through winding 30 of the contact making ammeter 29 and the coil 46 of the contact making instrument 44, to the control circuit 53 which extends through substations 6 and 7. Similarly, the positive side of the generator 36 is connected, through the coil 45 of the contact making instrument 44 to the control circuit 54, which also extends through substations 6 and 7. The coil 47 of the contact making instrument 44 is so arranged with respect to the coils 45and 46 that it tends to assume a position where the rotative forces exerted thereon by the magnetic fields set up by the coils 45 and 46 are equal and opposite.

This position of equilibrium will,of course, depend upon the relative number of turns in the .coils 45 and 46 and the relative values of the currents therein. In each of the substations 6 and 7 there is located regulating apparatus for causing current, proportional to the product of the voltages and the watt components of the currentsin the leadingin conductors, toflow in the control circuit 5.3, and regulating apparatus for causing current, proportional to the product of the voltages and the wattless components of the currents in the leading-in conductors, to flow in control circuit 54. The regulating apparatus at the" several substations is identical, and corresponding elements at the several stations are designated by the same reference numbers so that the regulating apparatus at substation 6- alone re'qui-res detailed explanation. Referring, therefore,.to

substation 6, 56 denotes regulating apparatus for causing current, proportional to the product of the voltages and watt components of the currents in the leading-in con ductors 8, to flow in control circuit53, and 57 denotes regulating apparatus for causing current, proportional to the product of the voltages and wattless components of the currents in the leading-in conductors 8, to flow in control circuit 54. The regulating apparatus 56 comprises a rotatably mounted spindle 58, a contact member 59 carried thereby, stationary contacts 60 and 61 cooperating with contactmember 59, a reversible motor 62, provided with a source of current 63 and controlled by the contact member 59 and the stationary contacts 60 and 61,

and a rheostat 64 having a resistance 65 and'a controller arm 66 operated by said motor. The spindle 58 is under the joint control of wattmeter elements 67 comprising windings suitably connected to theconductors 8 intermediate the" connection thereto of the feeder mains 2 and the feeder mains 18, and a current responsive device 68, comprising an electromagnet 69, having a winding connected, in series with the resistance 65 of the rheostat 64, between the control circuit 53 and the return conductor 55, and an armature 70 carried by the spindle 58 and operated by the electromagnet 69. The wattmeter elements 67 and the current responsive device 68 tend torotate the spindle 56 in opposite directions.

The regulating apparatus 57 comprises a rotatably mounted spindle 71, a contact mem-'v ber '72 carried thereby, stationary contacts 73 and 74 cocperating with contact member 72, a reversible motor 75, provided with a source of current 76 and controlled by the contact member 72 and the stationary contacts 73 and 74, and a rheostat 77, having a resistance 78 and a controller arm" 79 operated by said motor. 'The spindle 71 is under the joint control of reactive-volt ampere elements 80 comprising windings, suitably connected to conductors 8 intermediate the 'connection thereto of the feeder mains 2 and the feeder mains 18, and a current responsive device 81, comprising an electromagnet 82,

having a winding connected in series with A magnet 82 The reactive-volt ampere elements and the current responsive device 81 tend to rotate the spindle 71 in opposite directions. As illustrated, the reactive-volt ampere elements 80 comprise a current winding connected in one phase and a voltage winding connected across the other two phases of the leading-in conductors 8, so that the torque exerted upon the spindle 71 by the reactive-volt ampere elements 80 will be proportional to the product of the wattless component of the current in one phase and the voltage across the other two phases.

7 The operation of the system shown in Fig. 1, as at present understood, is as follows:

Assume the transmission lines 4 to be energized from one or more generating stations 5, that steam station 12 is in operation, that the generator 36 is in operation, that the switches 3, 10, 11 and 17 are closed and that loads are being carried by both substation 6 and substation 7. The regulating apparatus 56 at the substation 6 W111 then operate to cause a current to flow from the control circuit 53 to the conductor 55 which will be proportional to the product of the voltages and spindle 58 by the current responsive device 68 is equal to the opposing torque exerted upon the spindle 58 by the wattmeter elements 67, because the torque exerted by the current responsive device 68 is proportional to the current flowing from control circuit 53 through the winding of the current responsive device 68 and resistance 65 of the rheostat 64 at station 6 and the torque exerted by the wattmeter elements 67 is proportional to the power supplied to the substation 6 from the transmission mains 4, or, in other words, is proportional to the product of the voltages and watt components of the currents in the leading-in conductors 8. Similarly the regulating apparatus 56 at substation 7 will operate-to cause a current to flow from control circuit 53 to the conductor 55 which will be proportional to the power supplied to substation 7 from the transmission mains 4, or in other words, to the product of the voltages and the watt components of the currents in the leading-in conductors 9. The current in the control circuit 53, therefore, will be equal to the sum of the currents flowing from control circuit. 53 to return conductor 55 and, hence, be proportional to the total power drawn the substations 6 and 7 from the transmission lines 4. At the same time the regulating apparatus 57 at substation 6 will operate to cause a currentto flow from the control circuit 54 to the conductor 55 which will be proportional to the product of the voltages and wattless components of the currents supplied to the substation 6. This will result through the operation of the rheostat 77 by the motor 75 until the torque exerted upon the spindle 71 by the current responsive device 81 is equal to the opposing torque exerted upon the spindle 71 by the reactivevolt ampere elements 80, at which time the current flowing from control circuit 54 through the operating winding of the electro magnet 82 of the current responsive device 81 and the resistance 78 of the rheostat 77 at station 6 will bear a given relation to the product of the current in one phase of the leading-in conductors 8 and the voltage in the other two phases thereof. Similarly the regulating apparatus 57 at substation 7 will operate to cause a current to flow from control circuit 54 to the conductor 55 which will be proportional to the product of the voltages and the wattless components of the currents supplied to substation 7. The current in the control circuit 54, therefore, will be equal to the sum of the currents flowing from control circuit 54 to return conductor 55at stations 6 and 7 and hence will be proportional to the product of the voltages and the wattless components of the currents supplied to the distribution system 1 from the transmission lines 4.

The ratio of the current in the control gircuit 53 to the current in the control circuit 54 will represent the tangent of the angle whose cosine equals the power factor of the load imposed upon the main source of alternating current by the distribution system. Since the currents in the control circuits 53 and 54 traverse the coils and 46 of the contact making instrument 44 the movable coil 47 thereof will tend to assume a posi- 'tion dependent upon the power factor and will regulate, by means of the contact 48 and the contacts 49 and 50, the motor 40 and in turn the rheostat 37 so as to vary the current in the field of the generator 14 in the manner necessary to maintain the power factor of the load imposed upon the transmission lines 4 by the distribution system 1 approximately constant. By varying the angular position of the member 51, the power factor which is maintained may be adjusted. The current in the control circuit 53 controls the operation of the contact that, when the current in the control circuit 53, which current is proportional to the total power supplied to the distribution. system 1 by the transmission lines- 4, increases, the

tension of the spring 22 is increased through the operation of the motor 25 and an additional amount of steam supplied to the turbine 13. The generator 14 will thereupon carry a greater portion of the load of the substations 6 and 7 and will limit the power supplied to the substations 6 and 7 by the transmission mains 4 to a predetermined maximum value. It will thus be seen that my invention is effective to maintain the power factor of the load imposed by the system 1 upon the transmission lines 4 approximately constant and also to limit the power supplied to the system 1 by the transmission mains 4 to a predetermined maximum value.

Referring now to Fig. 2, in which elements corresponding to' elements shown in Fig. 1 are similarly designated and, therefore, will not be again described, 84 denotes a substation having leading-in conductors 85 which are adapted to be connected to the feeder mains 2 by means of the switch 10. The leading-in conductors 85 are connected to suitable substation apparatus, illustration of which, for the sake of simplicity and clearness, is omitted from the drawing, the legent load being applied to the substation terminals of the leading-in conductors 85 instead. 86 denotes a power factor indicating instrument comprising fixed coils 87 and 88, which are preferably angularly displaced ninety degrees, and a pivotally. mounted polarized armature 89 cotiperating therewith. The armature 89 is provided with a pointer 90 which plays over the scale 91. 92 denotes a double scale ammeter. 93 and 94 denote control circuits having .a common return conductor 95. 96 and 97 denote generators, the armatures of which are connected in series betweenconductors 98 and 99. To a point intermediate the armatures is connected the common return conductor 95. The coil 87 and the ammeter 92 are connected in series with the control circuit 93 whereas the coil 88 is connected in series with the control circuit 94. 100 denotes regulating apparatus for causing current proportional to the product of the voltages and the watt components of the currents in the leading-in conductors 85 to flow in the control circuit 93, and 101 denotes regulating apparatus for causing current proportional to the product of the voltages and the wattless components of the currents in the leading-in conductors 85 to flow in control circuit 94. The regulating apparatus 100 comprises a rotatably mounted spindle 102, a contact member 103 carried thereby, stationary contacts 104 and 105 cooperating with contact member 103, a reversible motor .106, provided with a source of current 107 and controlled by the contact member 103 and the stationary contacts 104 and 105, and a rheostat 108 comprising a resistance 109, to distributed points on which are connected contact buttons 110, contact segments 111 and 112, and a controller arm 113, which is operated by said motor and is adapted, under certain conditions, to connect contact segments 111 or 112 with corresponding contact buttons 110. The spindle 102 is under the joint control of wattmeter elements 114, comprising windings suitably connected to the leading-in conductors 85 and a current responsive device 115 comprising electromagnets 116 and 117 and an armature 118 carried by the spindle 102 and operated by electromagnets 116 and 117. The resistance 109 of the rheostat 108 is connected'between the conductors 98 and 99. The contact segment 111 is connected through the operating winding of the electroma et 116 to the control circuit 93, whereas t e contact segment 112 is connected through the operating winding of the electromagnet 117 to the control circuit 93. The wattmeter elements 114 and the current responsive device tend to rotate the-spindle 103 in opposite directions. The regulating apparatus 101 comprises a rotatably mounted spindle 120, a contact member 121 carried thereby, stationary contacts 122 and 123 cooperating with contact member 121, a reversible motor 124, provided with a source of current 125 and controlled by the contact member 121 and the stationary contacts 122 and 123, and a rheostat .126 comprising a resistance 127, to distributed points on which are connected contact buttons 128, contact segments 129 and 130, and a controller arm 131 operated by the motor 124 and adapted, under certain conditions, to connect contact segments 129 and 130 with corresponding contact buttons 128. The spindle 1201s under the joint control of the reactive-volt ampere element 132, comprising windings suitably connected to the leading-in conductors 85, and a current responsive device 133, comprising electromagnets 134 and 135 and an armature 136 carried by the spindle 120 and operated by the electromagnets 134 and 135. The resistance 127 of the rheostat126 is connected between the conductors 98 and 99. The contact segment 129 is connected through the operating winding of the electromagnet 134 to the control circuit 94 and the contact segment 130 is connected through the operating winding of the electromagnet 135 to the control circuit 94. The reactivevolt ampere element 132 and the current responsive device 133 tend to rotate the spindle 120 in opposite direction. As illustrated, the reactive-volt ampere element 132 com.

portional to the product ofthe wattless component of the current in the one phase and the voltage across the other two phases. Although the apparatus at only one substation' is illusrated, it should be understood that similar apparatus will be located at other substations included in the distribu tion system and that the control circuits 93 and 94 and the conductors 98 and 99 will extend through all such substations.

The operation of the system shown in Fig. 2, as at present understood, is as follows:

Assume the transmission lines 4 to be energized from one or more. generating stations' 5, that the generators 96 and 97 are in operation and are developing approximately equal voltages, and that the switch 10 is closed. It will be noted that with the controller arms 113 and .131 of the rheostats 108'and 126 in the positions shown, in which positions they are in contact with buttons corresponding to the central points of the resistances 109 and 127, the potential at the controller'arms will be the same as the potential at the point intermediate the armatures of the generators 96 and 97 to which the conductor 95 isconnected. When the controller arm 131 is moved from mid-position in a counter clockwise direction and the controller arm 131 is moved from mid-position in a clockwise direction the potentials thereat will increase, whereas, when the controller arm 113 is moved from mid-position in a clockwise direction and the controller arm 131 is moved from mid-position in a counter clockwise direction the potentials thereat will decrease. If the transfer of energy is from the feeders 2 to the substation 84, the regulating apparatus 100 will operate to cause current to flow from the conductor 98 to the control circuit 93 which will be proportional to the product of the voltages and watt components oi the currents supplied to substation 84. This will result since the torque exerted on the spindle 102 by the wattmeter elements 114, which torque is proportional to the product of the-voltages and watt components of'the currents supplied to substation 84, will maintain engagements between the contact member 103 and the stationary contact 105, thereby efi'ecting counter clockwise movement of the controller arm 113 over the segment 111, until the current in the operating winding of the electromagnet 116 has such a value that the torque exerted by the current responsive device 115 uponthe spindle 102 balances the to que exerted by the wei tmeter elements 114. Similarly if the transfer of energy is from substation 84 to the feeders 2, the regulating apparatus 100 will operate to cause current to flow from the control circuit 93 to the conductor 98. This will result since the torque exerted on the spindle 102 by the wattmeter elements 114 will maintain engagement between the contact member 103 and the stationary contact 104, thereby effecting clockwise movement of the controller arm 113 over the segment 112, until the current in the operating winding of the electromagnet 117 has such a value that the torque exerted by the current responsive device 115 upon the spindle 102 balances the torque exerted by the wattmeter elements 114. It will thus be noted that the direction of that portion of the currentin control circuit 93 which traverses the substation 84 is reversed in direction upon a reversal of the direction of energy transfer. By the use of two electromagnets 116 and 117, the reversal of the torque exerted upon the spindle 102 by the current responsive device 115 may be accomplished without making the armature 118 polarized. If the transfer of energy is fromthe feeders 2 to the substation 84 and the power factor of the load is lagging or, if the transfer of energy is from substation 84 to the feeders 2 and the power factor of the load is leading,

" the regulating apparatus will operate to cause current to flow from the conductor 98 to the control circuit 94 which will be proportional to the product of the voltages and wattless components of the currents in the conductors 85. This will result since under the conditions referred to the torque exerted on the spindle 120 by the reactive-volt ampere elements 132, which torque is proportional to the product of the voltages and wattless components of the currents in the conductors 85, will maintain engagement between the contact member 121 and the stationary contact 123, thereby effecting clockwise movement of the controller arm 131, until the current in the operating wind-' ing of the electromagnet 134 has such a' value that the torque exerted by the current responsive device 133 upon the spindle 120 balances the torque exerted by the reactivevolt ampere elements 132. If, however, the transfer of energy vis from the feeders 2 to the substation 84 and the power factor of the load is leading, or if the transfer of energy is from the substation 84 to the feeders 2 and the power factor of the load is lagging, the regulating apparatus 101 will operate to cause current to flow from the control circuit 94 to the conductor 99, which will be proportional to the product of the voltages and wattless components of the currents in the conductors 85. This will result because the torque exerted upon the ments 132, which torque is proportional to the product of the voltages and wattless components of the currents in the conductors 85, will maintain engagement between the contact member 121 and the stationary contact 122, thereby effecting a counter clock wise movement of the controller arm 131, until the current in the operating winding of the electromagnet 135 has such a value that the torque exerted by the current responsive device 133 upon the spindle 120 balances the torque exerted by the reactivevolt ampere elements 132. When a plurality of substations are employed and connected in the same manner as substation 84, the current in control circuit 93 will be proportional to the algebraic sum of the products of the voltages and watt components of the currents in the leading-in conductors at the several substations, whereas the current in the control circuit 94 will be proportional to the algebraic sum of the products of the voltages and the wattless components of the currents in the leading-in conductors at the several substations. The current in the control circuit 93 will, therefore, be proportional to the total power supplied to or re-. turned by the distribution system, whereas the ratio of the current in the control circuit 93. to the current in the control circuit 94 will represent the tangent of the angle, whose cosine equals the power factor of the load imposed upon the source by the distribution system or the power factor of the load imposed upon the distribution system when it is returning power. Since the current in the control circuit 93 traverses the ammeter 92, the indication thereof will represent the amount of power being supplied to the distribution circuit or the amount of power being returned by the distribution system. Furthermore, since the current in the control circuit 93 traverses the stationary coil 87 of the power factor instrument 86 and the current in the control circuit 94 traverses the stationary coil 88, the positions assumed by the armature 89 and the pointer 90 will depend upon the direction of transfer of energy between the distribution system and the source of alternating current supply and also upon the power factor of the load imposed upon the source of alternating current sup ly by the distribution system, or in case the distribution system is regenerating, upon the power factor of the load imposed thereon. When energy isbeing transferred from the source of alternating current supply to the distribution system, the pointer 90 will play over the quadrant a of the scale 91 of the power factor indicating instrument 86, if the power factor of the load is'lagging, and over the quadrant I), if the power factor of the load be leading. On the other-hand, if the distribution system be regenerating and, therefore, returning en ergy to the source the pointer will play over the quadrant c, if the power factor of the load imposed upon the distribution system be lagging, and over the quadrant d, if the power factor of the load be leading.

While we have herein shown and described two applications and modifications of our invention, We do not desire to be limited to the exact arrangements shown but seek to cover in the appended claims all those applications and modifications which come within the true spirit and scope of our invention. I

What we claim as new andfdesire to secure by Letters Patent of the ,United States, is

1. In combination, a source of alternating current, a distribution system, comprising a plurality of branch load circuits, supplied therefrom, and means responsive to electrical conditions in said branch circuits arranged to vary its position in accordance with the power factor of the load imposed upon said source by said system.

2. In combination, a source of alternating current, a distribution system supplied therefrom, a pair of control circuits, means for supplying current to said control circuits, automatic means for maintaining a ratio between the cugrents in said circuits approximately equal to the ratio of the product of the voltages and watt components to the product of the voltages and wattless components of the currents supplied to said system by said main source, and means responsive to the currents in said circuits arranged to vary its position in accordance with the power factor of the load imposed upon said source by said system.

3. In combination, a source of alternating current, a distribution system comprising a plurality of branch load circuits supplied therefrom, a pair of control circuits, means for supplying current to said control circuits, means responsive to electrical conditions in said branch circuits for maintaining a ratio between the currents in said control circuits approximately equal to'the ratio of the product of the voltages and watt components to the product of the voltages and wattless components of the currents supplied to said system by said source, and means responsive to the ratio of the currents in said control circuits arranged to vary its position in accordance with the power factor of the load imposed upon said source by said system. g

4. In combination, a main source of alternating current; a supplemental source of alternating current, a distribution system supplied from said sources, and automatic means for regulating said supplemental source to maintain the power factor of the load imposed upon said main source'by said system approximately constant.

5. In combination, a main source of alternating current, a supplemental source of alternatin current, a distribution system supplied rom said sources, and automatic means for regulatingv said supplemental source. to maintain the power factor of the loadimposed upon said main source by said system approximately constant and to limit the power supplied to said circuit by said main source to a predetermined maximum.

6. In combination, a main source of alternating current, a supplemental source of alternating current comprising generating means, a distribution system supplied from said sources, and automatic means for regulating the excitation of said generatmg means tomaintain the power factor of the load imposed upon said main source by said system approximately constant.

7. In combination, a main source of alternating current, a supplemental source of alternating current comprising generating means and driving means, a distribution system supplied from said sources, and air tomatic means for regulating the excitation of said generating means and for regulating the power supplied to said driving means to maintain the power factor of the load imposed upon said main source b said system approximately constant an main source to a predetermined maximum.

8. In combination, a main source of alternating current, a supplemental source of alternating current, a distribution system supplied from said sources, a pair of control circuits, means for supplying current to said control circuits,'automatic means for maintaining a ratio between the currents in said circuits equal to the ratio of the products of the voltage and watt component to the product of the voltage and wattless component .of the current supplied to said system by said main source, and means responsive to the currents in said circuits for regulating said supplemental source to maintain the power factor of the load imposed upon said main source by said system approximately constant.

9. In combination, a source of alternating current, a distribution system supplied therefrom, a pair of control circuits, means for regulating an electrical condition of one of said. circuits in accordance with a function of the'product of the voltageand the watt component of the current supplied to said system by said source, and means for regulating an electrical condition of the other of said circuits in accordance with ,a function of the product of the voltage and the wattless component of the current supplied to said system bysa'id source.

10. In combination, a source of alternating current, a distribution system supplied therefrom, a pair of control circuitavmeans to limit the power supplied to said system by said function of the product of the voltage and the watt component of the current supplied to said system by said source, and means for regulating the current in the other ofsaid circuits in accordance with a function of the product of the Voltage and the wattless component of the current supplied to said system of said source.

11. In combination, a source of alternating current, a distribution system supplied therefrom, a pair of control circuits, means for supplying currents to said control circuits, meansv for regulating the current in one of said circuits in accordance with the product of the voltage and the Watt component of the current supplied to said system by said source, means for regulating the current in the other of said circuits in accordance with the product of the voltage and the wattless component of the current supplied to said system'by said source, and a device responsive to the ratio of the currents in said circuits.

12. In combination, a source of alternating current, a distribution system supplied therefrom, a pair of control circuits, means for supplying currents to said control circuits, means for regulating the current in one of said circuits in accordance with the product of the voltage and the watt component of the current supplied to said system by said source, means for regulating the current in the other of said circuits in accordance with the product of the voltage and the wattless component of the current supplied to said system by said source, and a device responsive to the ratio of the currents in said circuit arranged to vary its position in accordance with the power factor of the load imposed upon said source by said system.

13. In combination, a source of alternating current, a distribution system supplied therefrom, a pair of control circuits, means for supplying currents to said con trol circuits, means for regulating the current in one of said circuits. in accordance with the product of the voltage and the watt component of the current supplied to said system by said source, means for regulating the current in the other of said circuits in accordance with the product of the voltage and the wattless component of the current supplied to said system by said source, and a device responsive to the ratio of the currents in said circuit for controlling the power factor of the load imposed upon said source by said system.

14. In combination, a main source of al ternating current, a supplemental source of alternating current, a distribution system supplied from said sources, a pair of control circuits, means for supplying current to said control circuits, automatic means for regulating the current in one of said'circuits in accordance with the product of the voltage and the Watt component of the current supplied to said system by said main source and for regulating the current in the other of said circuits in accordance with the product of the voltage and the wattless component of the current supplied .to said system' by said main source, means responsive to the current in the first mentioned circuit for regulating said supplemental source to limit the power supplied to said system by said main source to a predetermined maximum, and means responsive to the ratio of the currents in said circuits for regulating said supplemental source to maintain the power factor of the load imposed upon said main source by said system approximately constant.

15. In combination, a main source of alternatng current, a supplemental source of alternating current comprising generating means, a distribution system supplied from said sources, a pair of control circuits, automatic means for regulating the current in one of said circuits in accordance with the product of the voltage and the watt component of the current supplied to said sys tem by said main source and for regulating the current in the other of said circuits in accordance with the product of the voltage and the wattless component of the current supplied to said system by said main source, and means responsive to the ratio of the currents in said circuits for regulating the excitation of said generating means.

16. In combination, a main source of alternating current, a supplemental source of alternating current comprising generating means and driving means, a distribution system supplied from said sources, a pair of control circuits, means for supplying current to said control circuits, automatic means for regulating the current in one of said circuits in accordance with the product of the voltage and the watt component of the current supplied to said system by said main source and for regulating the current in the other of said circuits in accordance with the product of the voltage and the wattless component of the current supplied to said sys torn by said main source, means responsive to the current in the first mentioned circuit for regulating the power supplied to said driving means, and means responsive to the ratio of the'currents in said circuits for regulating the excitation of said generating means.

17. In combination, a main source of alternating current, a supplemental source of alternating current comprising generating means, a distribution system comprising a plurality of stations supplied from said sources, a pair of control circuits, and a return circuit extending between said suplemental source and said stations, means or supplying current to said circuits, automatic means for causing currents to flow between one of said control circuits and the return circuit at the several stations in accordance with the product of the voltage and the watt component of the current supplied thereto by said main source and for causin' currents to flow between the other of sai control circuits and the return circuit at the several stations in accordance with the product of the ,voltage and the wattless component of the current supplied 115 set our hands this 16th day of April, 1919.

JAMES R. CRAIGHEAD. v HENRY R. SUMMEBHAYE-S.

In witness whereof, .we have hereunto 2o 

